GCSE ADDITIONAL SCIENCE / BIOLOGY

Transcription

1 AQA Qualifications GCSE ADDITIONAL SCIENCE / BIOLOGY BL2HP Mark scheme 4405 / 440 June 204 Version:.0 Final

2 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students scripts: alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Assessment Writer. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students reactions to a particular paper. Assumptions about future mark schemes on the basis of one year s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this Mark Scheme are available from aqa.org.uk Copyright 204 AQA and its licensors. All rights reserved. AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre.

3 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 Information to Examiners. General The mark scheme for each question shows: the marks available for each part of the question the total marks available for the question the typical answer or answers which are expected extra information to help the Examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. The extra information is aligned to the appropriate answer in the left-hand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right-hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent. 2. Emboldening 2. In a list of acceptable answers where more than one mark is available any two from is used, with the number of marks emboldened. Each of the following bullet points is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for a mark are indicated by the use of or. Different terms in the mark scheme are shown by a / ; eg allow smooth / free movement. 3. Marking points 3. Marking of lists This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general principle to be followed in such a situation is that right + wrong = wrong. Each error / contradiction negates each correct response. So, if the number of error / contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (indicated as * in example ) are not penalised. Example : What is the ph of an acidic solution? ( mark) Student Response Marks awarded green, red*, 5 3 red*, of 3

4 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 Example 2: Name two planets in the solar system. (2 marks) 3.2 Use of chemical symbols / formulae Student Response Marks awarded Neptune, Mars, Moon 2 Neptune, Sun, Mars, Moon 0 If a student writes a chemical symbol / formula instead of a required chemical name, full credit can be given if the symbol / formula is correct and if, in the context of the question, such action is appropriate. 3.3 Marking procedure for calculations Full marks can be given for a correct numerical answer, without any working shown. However, if the answer is incorrect, mark(s) can be gained by correct substitution / working and this is shown in the extra information column or by each stage of a longer calculation. 3.4 Interpretation of it Answers using the word it should be given credit only if it is clear that the it refers to the correct subject. 3.5 Errors carried forward Any error in the answers to a structured question should be penalised once only. Papers should be constructed in such a way that the number of times errors can be carried forward are kept to a minimum. Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation e.c.f. in the marking scheme. 3.6 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term. 3.7 Brackets (..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 3.8 Ignore / Insufficient / Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. 4 of 3

5 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 Quality of Written Communication and levels marking In Question 2 students are required to produce extended written material in English, and will be assessed on the quality of their written communication as well as the standard of the scientific response. Students will be required to: use good English organise information clearly use ialist vocabulary where appropriate. The following general criteria should be used to assign marks to a level: Level : basic Knowledge of basic information Simple understanding The answer is poorly organised, with almost no ialist terms and their use demonstrating a general lack of understanding of their meaning, little or no detail The spelling, punctuation and grammar are very weak. Level 2: clear Knowledge of accurate information Clear understanding The answer has some structure and organisation, use of ialist terms has been attempted but not always accurately, some detail is given There is reasonable accuracy in spelling, punctuation and grammar, although there may still be some errors. Level 3: detailed Knowledge of accurate information appropriately contextualised Detailed understanding, supported by relevant evidence and examples Answer is coherent and in an organised, logical sequence, containing a wide range of appropriate or relevant ialist terms used accurately. The answer shows almost faultless spelling, punctuation and grammar. 5 of 3

6 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 (a)(i) amino acid(s) accept peptide(s) do not allow polypeptide(s) AO 2.5.2e (a)(ii) protease AO 2.5.2e (b)(i) 2 AO b, g (b)(ii) repeat do not allow other enzyme / substrate AO b using smaller ph intervals between ph and ph3 allow smaller intervals on both sides of / around ph2 allow smaller intervals on both sides of / around answer to (b)(i) (b)(iii) enzyme / pepsin denatured / shape changed enzyme / pepsin no longer fits (substrate) do not allow enzyme killed allow enzyme destroyed allow enzyme / pepsin does not work 2.5.2a, b (c) hydrochloric (acid) allow phonetic spelling accept HCl allow HCL ignore hcl do not allow incorrect formula e.g. H 2 Cl / HCl 2 AO 2.5.2g Total 8 6 of 3

7 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information on page 5 and apply a best-fit approach to the marking. 0 marks Level ( 2 marks) Level 2 (3 4 marks) Level 3 (5 6 marks) No relevant content. An example is given of a named substance or a process or there is an idea of why diffusion is important eg definition. examples of points made in the response Importance of diffusion: to take in substances for use in cell processes products from cell processes removed Examples of processes and substances: for gas exchange / respiration: O 2 in / CO 2 out for gas exchange / photosynthesis: CO 2 in / O 2 out food molecules absorbed: glucose, amino acids, etc water absorption in the large intestine water lost from leaves / transpiration water absorption by roots mineral ions absorbed by roots At least one example of a substance is given and correctly linked to a process in either animals or plants. extra information 6 There is a description of a process occurring in either animals or plants that is correctly linked to a substance and a process occurring in the other type of organism that is correctly linked to a substance. Description of processes might include: movement of particles / molecules / ions through a partially permeable membrane (movement of substance) down a concentration gradient osmosis: turgor / support / stomatal movements AO 2..2a,b, c, 2.2.d, 2.3.a,b, c,g, 2.6. Total 6 7 of 3

8 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 3(a) anaerobic respiration allow phonetic spelling AO 2.6.2a, b,d 3(b)(i) , 4.3, 4.5 or 4.6 with figures in tolerance (6.7 to 6.9 and 2.3 to 2.5) and correct working gains 2 marks 4.2, 4.3, 4.5 or 4.6 with no working shown or correct working with one reading out of tolerance gains mark correct readings from graph in the ranges of 6.7 to 6.9 and 2.3 to 2.5 but no answer / wrong answer gains mark a, b,d 3(b)(ii) more energy is needed / used / released (at 4 km per hour) not enough oxygen (can be taken in / can be supplied to muscles) do not allow energy production ignore work allow reference to oxygen debt do not allow less / no oxygen 2.6.2a, b,d so more anaerobic respiration (to supply the extra energy) or more glucose changed to lactic acid allow not enough aerobic respiration Total 6 8 of 3

9 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 4(a)(i) any one from: can supply correct nutrients can supply optimum concentrations / amount of nutrients can maintain optimum ph allow plants get enough (of required) nutrients ignore monitoring allow ions not lost / not wasted allow less chance of disease 2.3.g, 2.4.a 4(a)(ii) provides oxygen (oxygen) for (aerobic) respiration (respiration) supplies energy (for the roots) do not allow if extra gases or substances are given do not allow anaerobic allow use of energy eg for active uptake of ions 2.6.b,e, 2.4.a 4(b)(i) plants can take in high amounts of all ions at this ph allow the most ions taken up ignore reference to thickness of bars AO3 2.3.g allow easier / easiest or faster / fastest 4(b)(ii) (to make chlorophyll which) traps light / energy 2.3.b for photosynthesis / for making food / for making organic substances allow correct named example eg glucose / starch 4(b)(iii) nitrate allow NO + 3 / NH 4 / ammonium ignore nitrite AO 2.3.g 4(b)(iv) to make protein / amino acids / enzymes allow other correct example eg DNA / ATP / chlorophyll / auxin AO 2.3.g Total 9 9 of 3

10 MARK SCHEME GCSE ADDITIONAL SCIENCE / BIOLOGY BL2HP JUNE 204 5(a)(i) to get data re position of seaweed / of organism 2.4.b in relation to distance from sea / distance down shore / how long each seaweed was exposed 5(a)(ii) repeat several times elsewhere along the shore minimum = 2 repeats AO (a)(iii) bladder wrack is further up the shore (than the sea lettuce) / exposed for longer sea lettuce (only) in rock pools / in the sea / (only) in water ignore found in dry areas / on bare rock AO3 2.4.a,b 5(b) gets more light / closer to light (so) more photosynthesis allow better access to CO 2 allow mark for light for photosynthesis 2.4.a, 2.3.c allow mark for CO 2 for photosynthesis ignore reference to oxygen for respiration more only needed once for 2 marks Total 8 0 of 3

11 MARK SCHEME GCSE ADDITIONAL SCIENCE / BIOLOGY BL2HP JUNE 204 6(a)(i) one form of a / one gene do not allow a type of gene 6(a)(ii) not expressed if dominant / other allele is present / if heterozygous or allow a mutation of a gene allow need two copies to be expressed / not expressed if only one copy / only expressed if homozygous AO 2.7.2c,e, 2.7.3a AO 2.7.2c,e, 2.7.3a 6(b)(i) 6(b)(ii) only expressed if dominant allele not present / or no other allele present two parents without PKU produce a child with PKU / 6 and 7 0 genetic diagram including: Parental gametes: 6: N and n and 7: N and n allow it skips a generation AO3 2.7, 2.7.3a accept alternative symbols if defined / AO3 2.7, 2.7.3a derivation of offspring genotypes: NN Nn Nn nn allow genotypes correctly derived from student s parental gametes identification: NN and Nn as non- PKU OR nn as PKU allow correct identification of student s offspring genotypes correct probability only: 0.25 / ¼ / in 4 / 25% / : 3 do not allow 3 : / : 4 do not allow if extra incorrect probabilities given 6(c)(i) mitosis correct spelling only AO 2.7.a,c,d 6(c)(ii) c,i, 2.7.3a, 2.7.3d 6(c)(iii) DNA allow deoxyribonucleic acid do not allow RNA / ribonucleic acid AO 2.7.2g, 2.7.3a, 2.7.3d of 3

12 MARK SCHEME GCSE ADDITIONAL SCIENCE / BIOLOGY BL2HP JUNE 204 6(d)(i) may lead to damage to embryo / may destroy embryos / embryo cannot give consent allow avoid abortion allow emotive terms eg murder religious argument must be qualified allow ref to miscarriage allow idea of avoiding prejudice against disabled people allow idea of not producing designer babies AO3 2.7, 2.7.3a 6(d)(ii) any one from: prevent having child with the disorder / prevent future suffering / reduce incidence of the disease embryo cells could be used in stem cell treatment ignore ref to having a healthy child ignore ref to selection of gender AO3 2.7, 2.7.3a allow ref to long term cost of treating a child (with a disorder) allow ref to time for parents to become prepared Total 2 2 of 3

13 MARK SCHEME GCSE Additional Science / Biology BL2HP JUNE 204 7(a) lack of fossils / fossils destroyed (due to soft parts) decaying / geological activity allow lack of evidence allow an example eg vulcanism or earth movements or erosion allow converse points re skeletons, shells, hard parts AO 2.8, 2.8. a,b,c 7(b)(i) A and B did not mate successfully A and B did not mate insufficient allow did not produce fertile offspring 2.8.f 7(b)(ii) any two from: may not be mating season A and B may not find each other attractive this is just a one-off attempt / an anomaly / need repeats may be juvenile / immature may be the same sex allow other sensible suggestion eg were put in unfavourable environment or one / both could be infertile 2 AO3 2.8.f 7(c). (two ancestral populations) separated (by geographical barrier / by land) / were isolated 2. genetic variation (in each population) or different / new alleles or mutations occur 3. different environment / conditions 4. natural selection occurs or some phenotypes survived or some genotypes survived 5. (favourable) alleles / genes / mutations passed on (in each population) 6. eventually two types cannot interbreed successfully allow abiotic or biotic example allow eventually cannot produce fertile offspring 2.8.f Total 3 of 3